Photomorphogenic reactions in geranium (Pelargonium x hortotum) plants stimulated by brief exposures of ultraviolet-C irradiation

Abstract

Of all environmental factors that influence plant growth and development, light and other regions of the electromagnetic spectrum are most essential. In the present study, the effects of ultraviolet-C (UV-C) irradiation on two cultivars, Victor and Glacis, of pot grown geranium (Pelargonium x hortotum) plants were evaluated. Two-year experimental data showed that low doses of UV-C (i.e. 0.5–5.0 kJ m−2) irradiation led to photomorphogenic changes recorded as increases of fresh and dry weight, number of lateral stems and number of inflorescences formed. Although changes were recorded for both cultivars, responses to UV-C were population dependent with cv. Glacis appearing to be the more responsive one. The number of inflorescences formed on UV-C irradiated cv. Glacis plants was significantly (P < 0.05) higher to that of the non-irradiated controls throughout the pot trials in 2010 and 2011. For example, in the 2010 pot trial, exposure to 2.5 kJ m−2 UV-C resulted in the increase of inflorescences by 75 %. Additionally, the number of lateral stems on UV-C irradiated plants of cvs. Victor and Glacis increased by 122 % and 64 %, respectively. Temperatures and PARs during the 2-year pot trials varied to a considerable level and seem to have affected floral development and growth of both cultivars. However, only in cv. Glacis the effect on floral development was significant as cv. Victor geraniums grown in 2010 and 2011 showed comparable numbers of inflorescences. Our results show that brief exposures of geranium plants to UV-C may facilitate the production of high quality final products in a cost effective and environmentally friendly way.